In reply to Andypeak:
It's pretty easy to tell if they are the same or not (they aren't). Thanks to the EU, you can look up their ingredients right on Nikwax websites (EU and UK ones, not the US one, obviously!) or the EU databases for cosmetics.
Tech Wash: Aqua, Sodium Cocoate, Lauryl Glucoside, Sodium Oleate, Caprylyl/Capryl Glucoside, 2-Ethylhexyl Glucoside, Sodium Carbonate, Tetrasodium Iminodisuccinate, Dispersion Based On Polyacrylates, Sodium Cumenesulfonate, Acrylate Homopolymer
Down Wash Direct: Aqua, Caprylyl/Capryl Glucoside, Sodium Cocoate, Lauryl Glucoside, Dimethiconol, Sodium Oleate, 2-Ethylhexyl Glucoside, Sodium Carbonate, Disodium Succinate, Tetrasodium Iminodisuccinate, Sodium Cumenesulfonate, Sodium Hydroxide, Zirconium Acetate, Acrylate Homopolymer, Sodium Acetate
I am no chemist, but it seems most of these are just various soaps/surfactants. The very few polymers seem to be suspending agents, to prevent dirt clumping together or settling out of the washing water?
The main difference seems to be Zirconium Acetate and few helper ingredients in Down Wash Direct, as Z.A. is used in some water repellency formulas. I guess Down Wash Direct adds some DWR to the down or fabric, while Tech Wash just cleans (kind of corroborated by their product description).
TL;DR: Tech Wash is just cleaner, Down Wash Direct adds water repellency. I'd think Down Wash Direct might work better on down (DWR), but either could work the same for cleaning only.